With the rapid development of an Internet Protocol (IP) network, a capacity and the number of users of an IP bearer network increase continuously and rapidly, leading to a greater demand for network bandwidth. To deal with the rapidly increasing demand for network bandwidth, a virtual cluster technology appears. The virtual cluster technology is virtualizing multiple network devices as a whole, and the multiple network devices are externally presented as one network device. A user may manage a cluster device on a management device of a virtual cluster, for example, perform configuration, install a patch, set a Product Adapter File (PAF), or set a license (license).
A management device in a virtual cluster is referred to as a main device, and a managed device is referred to an Access Point (AP). When an IP address is configured for each network device in the virtual cluster, data communication between the main device and the AP is performed by establishing a traffic engineering tunnel (Traffic Engineering Tunnel, TE Tunnel).
In actual networking, there may be a large number of network devices in a virtual cluster, and therefore, it may occur that multiple management devices manage the entire virtual cluster simultaneously, and each management device needs to save topology information in the entire virtual cluster. To achieve that each management device in the virtual cluster saves topology information of network devices in the entire virtual cluster, the prior art uses the following technical solution.
First, the network devices in the virtual cluster are categorized into multiple management domains in a manual configuration manner, where each management domain includes one management device, and the management device in each management domain manages other network devices in the management domain to which the management device belongs. The management device in each management domain collects topology information of network devices in the management domain, and topology information synchronization is performed among management devices of different management domains in the virtual cluster, thereby achieving that each management device in the virtual cluster saves topology information of the network devices in the entire virtual cluster. By performing topology information synchronization among network devices in each management domain, the management device in each management domain can obtain topology information of the network devices in the management domain to which the management device belongs. In the foregoing technical solution, before topology information synchronization is performed among the network devices of each management domain, domain information needs to be manually pre-configured on each network device, and a neighbor relationship needs to be established. For example, if topology information synchronization needs to be performed between two network devices in a management domain in a virtual cluster, domain information needs to be configured on the two network devices first, and by using an example that obtaining domains by means of division is achieved by using an Intermediate System to Intermediate System (Intermediate System to Intermediate System, IS-IS), the following configuration needs to be performed on the two network devices separately:                isis 1;        is-level level-1; and        network-entity 10.0000.0000.0001.00.        
Then, after an IS-IS neighbor relationship is established between the two devices, topology information of the two devices is synchronized with each other. Because domain information needs to be manually configured on each network device, and a neighbor relationship needs to be established, difficulty in maintaining a virtual cluster is increased, which is adverse to the development of the virtual cluster technology.